1. Field of the Invention
The present invention relates to an image forming apparatus, and in particular relates to an image forming apparatus including a recording head or print head to discharge ink droplets and a head tank to supply liquid ink to the print head.
2. Description of the Related Art
As an image forming apparatus such as a printer, a facsimile machine, a copier, a plotter, and a multifunction apparatus combining capabilities of the above devices, an inkjet recording apparatus of a liquid discharging recording method employing a recording head formed of ink droplet discharging head is known.
JP-2001-207206-A discloses one type of image forming apparatus including a head tank or sub tank disposed at the recording head side to which liquid ink is supplied from a main tank during the printing operation. The head tank has a displacing member which displaces in response changes in the amount of ink remaining inside the head tank. A first sensor to detect that the displacing member is positioned at a predetermined first position is disposed at a carriage and a second sensor to detect that the displacing member is positioned at a predetermined second position is disposed at the apparatus body side. A displacement amount of the displacing member between the first position detected by the first sensor and the second position detected by the second sensor is detected and stored, and when the liquid is supplied from the main tank to the head tank without using the second sensor at the apparatus body side, after the first sensor has detected the displacing member, an amount of liquid corresponding to the difference is supplied to the head tank.
In the configuration disclosed above, a malfunction of the liquid supply might occur due to any one of several different factors, such as if the remaining amount of the liquid is small, if any trouble occurs in the fluid supply means, if the supply amount is less than the predetermined amount, or if there is a leak in the supply system.